A nanocomposite is a material made by hybridizing mutually different heterogeneous materials at a nanoscale level by a physical or chemical method in order to overcome a limitation of properties of a material made by simply combining homogeneous materials or heterogeneous materials and obtain synergistic effects on multi-function and high performance. The nanocomposite is divided based on types of a matrix and a filler. Here, a nanocomposite in which a polymer is used as a matrix is a composite which is prepared by uniformly dispersing a nanoscale filler in a polymeric resin and has excellent mechanical strength, an excellent gas barrier property, and greatly improved abrasion resistance and thermal resistance. When a composite is prepared by charging a polymeric resin with a nanoscale filler, even with a small amount of a filler, properties are greatly improved, compared to a polymer composite prepared by charging a polymeric resin with a microscale filler.
A polymer nanocomposite based on such excellent properties has attracted attention as new materials that are expected to be applied in fields such as the automobile industry, the electronics industry, the energy industry, and the like, all of which require a highly functional composite. Currently, research on the development of a high functional polymer nanocomposite prepared by charging a polymeric resin with carbon-based fillers such as carbon nanotubes, carbon fibers, graphene, and the like has been actively conducting. Among them, flaky graphite has currently attracted the most attention as a filler.
Carbon nanostructures such as flaky graphite and the like have advantages of having a large surface area, highly excellent mechanical strength, thermal and electrical properties, flexibility, and transparency, compared to other conventional nanoadditives (such as Na-MMT, LDH, CNT, CNF, EG, etc.). Therefore, currently, research on the development of a high performance and functional polymer composite having excellent conductivity and mechanical strength, which is prepared by charging a polymeric resin with flaky graphite, has been actively conducting.
However, since carbon nanostructures such as flaky graphite and the like are difficult to be uniformly dispersed in a polymeric resin and an organic solvent due to van der Waals forces between them and a very stable chemical structure that they have, it is difficult to prepare a polymer composite exhibiting uniformity. As a result, although a carbon nanostructure itself has excellent properties, research on actually applicable technology is very limited.
For solving these problems, research on a method of modifying a surface so that a carbon nanostructure is capable of forming a uniformly dispersed phase in an organic solvent has been actively conducting.
In order to uniformly disperse a carbon nanostructure and increase a mutual affinity with a polymer, it is necessary to perform an additional pretreatment process on the surface of a carbon nanostructure. In a conventional method of preparing a complex, a functional group is introduced into a carbon nanostructure using a wet acid treatment method in order to improve dispersibility in a polymer, but the wet acid treatment method has disadvantages in that a yield of a treated carbon nanostructure is low and the method is not environmentally friendly.
In addition, there is a method of introducing a functional group on the surface after exposure to gases in a vacuum using plasma deposition, but the method has difficulty in a storing method of a carbon nanostructure. In this case, since the carbon nanostructure has been chemically etched, aging of a treated carbon nanostructure is accelerated to degrade intrinsic properties of a carbon nanostructure.
The present inventors first prepared a complex composed of flaky graphite, a catecholamine, and polymer layers, which has high cohesion with a polymer without degradation of intrinsic properties of flaky graphite by coating, i.e., by modifying a surface of, flaky graphite having a crystallized nanometal on the surface thereof with a catecholamine such as polydopamine and the like, and then confirmed that a composite having remarkably improved dispersibility in a target polymeric resin can be prepared as thus. Therefore, the present invention was completed based on this fact.